Power unit for hydraulic brakes



April 19,1949. J. R. ALMOND POWER UNIT FOR HYDRAULIC BRAKES 3 Sheets-Sheet 1 Filed Jan. 4, 1946 7 gar;

maxim" wall "m .2 o 2 d 0} m 17 f 7 f w z 0 mm M Tn l m an. 2 o *m 9M 5 o2 mm s m 5 mm 0 m m m2 mu 3 a 8 3 2 0 B h? n K Oh wv m 2 um I e m f 3 t Pm n5 3 a a s i s 02 o. 02 N WNRN INVENTOR. JOHN R. ALMOND ATTORNEY,

April 1949- J. R. ALMOND I POWER UNIT FOR HYDRAULIC BRAKES Filed Jan. 4, 1946 3 Sheets-Sheet 2 wwxcim O INVENTOR. JOHN R. ALMOND.

ATTORNEY.

April 19, 1949. J. R. ALMOND I 2,467,517

POWER UNIT FOR HYDRAULIC BRAKES I Filed Jan. 4, 1946, a sheets-sheet 3 mofN ATTORNEY Patented A r. 1a 1949 UNITED STAT S. PATENT John R. Almond. Cleveland, Ohio, assignor'to The Midland Steel Products Company, Cleveland, Ohio, a corporation of Ohio Application January 4, 1946, Serial No. 639,092

This invention relates to new and useful improvements in power operated hydraulic pressure units for vehicle brakes and an important object is to provide means for positively and automatically unloading the pressure created by the unit under certain conditions.

Another object of the invention is to provide a differential pressure motor for operating a hy draulic unit with an elongated thrust rod which is provided with means for accurately adjusting the operating relation between the motor and the unit to achieve proper phaseoperation.

A further object is to provide a double capacity fluid pressure motor from two individual motors and to provide means for reinforcing the motor with an extra symmetrical casing.

A still further object of the invention is to provide the power unit with means for maintaining a pressure condition in elongated hydraulic lines or pipes, such as exists from tractor to trailer and which will assure prompt actuation of the trailer brakes from the tractor control.

Another object is to improve the construction of such brake units to increase their power and range, and to provide for sensitivity, a safety factor and to provide for quick assembly in the manufacture of the units. v

Other objects and advantages will become apparent during the course of the following description. y

In the accompanying drawings forming a part of the description and wherein like numerals are employed to designate like parts throughout the several views,

Fig. 1 is a longitudinal vertical section through the unit taken on the line ll of Fig. 4,

Fig. la is an enlarged view of a portion of the apparatus of Fig. 1.

Fig. 2 is an enlarged longitudinal section of the hydraulic unit, i

Fig. 3 is a transverse section of the same taken on the line 3-3 of Fig. 2,

Fig. 4 is a top elevation of the power unit assembly with the hydraulically operated valve shown in section,

Fig. 5 is an enlarged longitudinal section 0 the upper portionof the sub-assembly of the power unit or motor,

Fig. 6 is an enlarged transverse section taken through part of the bottom of the power unit easing.

This invention is adapted to be used for operating the hydraulic brakes of tract-orand trailer vehicles, either where the hydraulic fluid is piped from the tractor to the trailer, or where the 10 Claims. (01. 60-545) 2 trailer is provided either with a separate hydraulic system or is equipped with the usual air or vacuum operated brakes controlled by a fluid medium piped from the tractor to the trailer in manners well understood in the art. The power unit for such systems is shown in the accompanying drawings andoons'ists broadly 01 a differential pressure motor ID for actuating the piston of a hydraulic unit cylinder unit I l to exercise the proper degree of pressure on the hydraulic fluid brakes of both the tractor and trailer. A differential fluid pressure control valve forms an integral part of the hydraulic cylinder H, to transmit variable degrees of fluid pressure mediumto the differential motor I 0. dependingupon the amount of hydraulic pressure created in the cylinder ll. Actuation of this power unit is dependent upon the usual hydraulic master cylinder 9, diagrammatically shown, transmitting fluid under pressure through a pipe iii to a compensating chamber l4 behind a' piston IS in the cylinder H as best seen in Fig. 2. This piston is skirted and communicates with the compensating chamber-l4 through radially arranged ports I6. I

The piston 15 is provided with a'central port I! aligned with a central aperture of the usual skirted rubber cup 18 opening into the bore or pressure chamber IQ of the cylinder ll. Thus. a depression of the foot pedal of the master cyl-- in-der 9 places fluid in the hydraulic cylinder ll under primary pressure transmitted to the hydraulic brake lines through the port 20 in the end of the cylinder II to take up slack in the'brakes 8 at the wheels, and if desired, to apply these brakes with manual pressure exercised upon the master cylinder. An embossed valve seat 2| surrounds the port ll to seat an elastic insert 22 of a valve 23 loosely slidable in the hollow piston l 5. This valve 23 is normally held off of its seat by a coil spring, as shown, in order thatfluid may pass from the compensating chamber l4 through the ports l6 and central port I! of the piston. A power piston rod 24 is slidably mounted in a bushing 25 plugging the end of the cylinder it so that upon a power actuation of the motor ii! the rod 24 will b projected to the right of Fig. 2 to force the valve 23 upon its seat. thereby closing the port I! and moving piston iii to the right of Fig. 2 in order to intensify the pressure of the having the port 20 therein to which the brake line is connected as shown in Figure 2. In this cap is of an inwardly opening valve cage 28 held seated on an elastic collar or seat 23 by means of a coil spring 30 which holds an amount of hydraulic pressure. depending upon the strength of the spring 30, in the brake line, when piston i is in brake release position. Where the hydraulic brake lines back to the trailer or tractor brakes are extremely long, this double check valve 28 serves to hold the brake line pressure at a predetermined quantity so as to eliminate any tendency of the brakes to lag during a brake application. The valve cage 28 is provided with lateral ports 3| which are closed by the skirt of a rubber plug 32 seated in the cage as shown, whenever the back pressure in the brake line exceeds that existing in cylinder i i. Any pressure in the brake line exceeding the strength of spring 30, when the piston is is retracted or is being retracted will cause the valve cage 28 to unseat and relieve brake pressure in the brake line to a degree determined by spring 30. or course, upon a power stroke of piston IS, the pressure of fluid will flex the skirt of valve 32 permitting fluid under pressure to pass through the ports 3| to the brake line. The spring 30 is held in the cap 21 by a snap ring 33 which also holds a perforated abutment disc 34 from movement in one direction, while a piston return spring 35 prevents movement of the disc in the opposite direction. Those parts in the cap 21 form a sub-assembly which can be removed and positioned as a unit. The opposite end of the return spring 35 seats in a metallic cup 38 in engagement with the rubber cup l8. Thus, it will be seen that piston return spring 35 has no abutment with the double check valve and therefore exercises no control over its movements. This is left entirely to the spring 30, the characteristics of which can be varied to alter the normal brake line pressure in any degree desired.

Secured over the central aperture in the metallic cup 36 and projecting axially thereof into cylinder ii is a perforated guide sleeve 31 having its outer end flanged or spun over an unloader valve rod 38 to form a sliding fit therewith. This unloader rod is provided with an enlargement 39 which slides freely in the guide sleeve 31 to guide the unloader rod through the port i'l in piston I! to engage and unseat the valve 23, after the piston l5 separates from the end of the rod 24 due to a liquid pressure build-up and the end of the unloader valve rod abuts the central imperforate portion of the limiting disc 34. The unloader rod is also useful in assuring the unloading of the system of hydraulic pressure when the brake lines are purged or bled with excessive pressure to advance piston [5, since the unloader located a double check valve consisting rod will kick the valve 23 open whenever the piston i3 separates from the rod 24 and nears the end of 'its projectile stroke, thereby freeing the brake lines of any tendency toward a locked condition, since the fluid under pressure ahead of piston i5 will be relieved through the opening of the valve 23. The free end of the unloader rod 38 is pinched or upset as at 40 to prevent accidental displacement of the rod when the metallic cup 36 is being placed in or removed from the cylinder II.

It will be understood that the extent of movement of rod 24 to the right, as viewed in Fig. 2, is so regulated that the rod cannot move piston II for enough to the right to cause unloader rod 40 to engage disk 34 and be moved through the piston to press against valve 23. The stroke of rod 24 is so regulated that when it has moved to its extreme right-hand position, as viewed in Fig. 2, the leading end of unloader rod 40 will preferably be just out of contact with disk 34. In no event is rod 24 capable of moving piston i5 far enough to the right, as viewed in Fig. 2, to bring rod 40 into engagement with disk 34 and force the rod into unseating engagement with valve 23.

The inner end of the hydraulic cylinder Ii is cast with an enlargement 42 to be secured to the flat end wall 43 of a convex stamping 44 forming a part of the motor ID, by means of the screw 45 clamping the flat wall between the enlarged end of the cylinder and a relatively thick steel plate 48 arranged on the inside of the stamping 54. This end wall 43 and reinforcing plate 46 have aligned openings at their centers through which a reduced portion of the bushing 25 extends with a shoulder in engagement with the end wall 43. A rubber skirted cup 41 is positioned in the compensating chamberi4 and bears against the inner end of the bushing 25 to prevent the leakage of fluid. The inner skirted end of the piston I5 is reduced to fit the groove in the rubber cup when the piston is in its retracted position as shown in Fig. 2. Inside of the hollow or skirted piston I5 is a limiting ring against which the valve 23 abuts when the valve is pushed into its fully opened position by a spring as shown. A. sealing member 50 surrounds the power piston rod 24 and is held against the end oi the bushing 25 inside of the motor stamping 44 by means of a stamped clip 5 l.

The integral enlarged portion of cylinder ii is provided with a plunger bore 52 communicating with the compensating chamber H by means of a diagonal bore 53 terminating in a bleeder screw 54. A hydraulic plunger 55 for operating the control valve 12 is reciprocable in the bore 52 and terminates in a hollow hub 5| to which a diaphragm 51 is attached; Thus the valve is subjected to pressures existing in the compensating chamber. This diaphragm divides the control valve into a control chamber 53 and a low pressure chamber 59, communication between which is had through a port 40 in the hub. The low pressure chamber 5! communicates with the inside of the motor stamping 44 by means of the duct M. The housing of the control valve is provided with a seat 62 upon which is normally engaged an air valve 43 fully disclosed in the aforesaid pending application. It will be apparent that the valve i2 is also subject to the operating pressures oi. the motor ii.

The motor or differential fluid pressure engine ill for power actuating piston I5 is composed primarily of two similar power chambers 65 and 6G hooked up in tandem for increased power. Cooperating with the deeper stamping 44 is a complementary cup-shaped stamping 31, both having their open ends terminating in corresponding outwardly extending annular flanges 68 between which is clamped the outer beaded edge of a diaphragm by means of a split inverted U-shaped clamping band 100. The inner beaded edge of the diaphragm is securely clamped between the beaded edges of a pair of complementary discs it having complementary radially embossed portions which reinforce and space the plates apart at their hub portions to be clamped upon a collar between a snap ring 1| and a nut 12 threaded upon the end of a hollow piston stem 12. The

hollow piston stem 13 is slidably mounted through a packing 14 and abushing 15 which is suitably grooved and flanged to clamp the edges of aligned openings in the casing stamping 81 and a flat wall 16 of a second convex stamping 11 forming part of the second tandem power chamber. The end wall of the stampingv 61 is more or less flat and is provided with radial reinforcing ribs 12 as best seen in Fig. 1. As shown in Fig. 5, the walls of the two stampings 11 and 61 are spot welded together as at 19 to form a sub-assembly and this is accomplished by bending a'flat sheet of metal 80 into the form of a cylinder to snugly fit around both stampings 61 and 11 to reinforce them and provide a symmetrical unit. The iongitudinal edges 8i of this strip of metal are drawn around the stampings as shown so that their edges are spaced apart as at 3| in Fig. 6 and are spot welded at intervals to the stampings as at 82 in order that any condensation between the stampings will drain.out.' In addition, the end edges of the strip 39 are spot welded at spaced intervals as at 82' to the two stampings 61 and thereby forming the sub-assembly complete as a unit.

A shallow cup-shaped stamping 85 similar to the stamping 61. cooperates with the convex stamping 11 in forming the second power chamber and these two stampings are similarly clamped upon the outer beaded edge of a second diaphragm 86. The inner beaded edge of the diaphragm is clamped between a pair of piston,

plates 10' similar to 10, and these are secured to the opposite end of the hollow piston stem 13 by means of the snap ring 81 and nut 88. The two pistons or diaphragms I0 and ii with the piston stem 13 are normally held in the release position shown in Fig. 1 by a coiled spring I03 abutting the bushing 15 at one end being held at its other and against the piston 10 by a disc having an ofi'set edge ltd. The stamping 85 is formed with a threaded stud 89 by which the power unit is secured to the chassis of the tractor and is also formed with a pipe connection 90 to which an L-shaped pipe connection 9| is connected thereto and to a T coupling 32 threaded into a nipple 93 secured to the power chamber stamping $1 extending through an aperture in the cylinder 80 as shown in Fig. 5. In order to connect the control valve with the T coupling 92, a pipe 96 extends therebetween as shown in Fig. 4, and if desired, an extension pipe 95 may be connected to this pipe to run to the controls on the trailer in case the trailer installation is equipped with hydraulic or vacuum brakes, whichever may be employed, and controlled in the latter case with the usual trailer relay valve. A source of low pressure such as vacuum from the intake manifold of the tractor is piped by means of conduit 96 through the motor stamping 44 in order to pass through the hollow piston stem 13 and thence out through apertures 91 into the second chamber 85. This low pressure is also simultaneously communicated through the port 6i to the low pressure chamber 59 of the valve and thence through the hollow hub 56 to control chamber 58, from whence it passes through pipes 94 and M into the chambers at the left side of the diaphragms to suspend the power unit or motor in vacuum, so that the various parts in brake release position assume the position shown in Figs. 1 and 2.

In order to achieve proper phase operation between the motor and the hydraulic piston IS, an adjustable plug IN is screwed into the end of control of the brakes.

or subtracting'shims losbetween the end of stem 13 and the flange of plug l0] the distance between the end of piston rod 24 and the hydraulic valve 23 can be altered so that this valve can be closed and pressure in the cylinder l5 can be initiated at any desired interval of time subsequent to the initiation of movement of the diaphragm and 86;

a From the foregoing description it will be apparent that when the brake pedal of the master cylinder 9 on the tractor is depressed, its initial movement will force liquid into the compensating chamber I 4' through the piston l5, check valve 28 and into the brake lines to take up whatever slack exists and to press the brake shoes to the drums. As hydraulic pressure in the compen- V sating chamber ll increases. it is transmitted to the valve plunger 55 to cause the hub of the valve to open the air inlet valve 63 whereby air at atmospheriepressure is admitted to the control chamber 58 and passes to the left hand sides of the diaphragms in the motor to move them to the right of Fig. 1. This motion is transmitted through the piston rod 24 to efiect closing of the hydraulic valve 23 and to compel forward movement of the hydraulic piston l5 thereby increasing hydraulic pressure in the cylinder l5 and hyj draulic linesto the brakes. Due to hydraulic pressures on both sides of piston I5, the valve l2 will be impressed at all times with the power input and power output of the device thereby rendering the diaphragm sensitive to those pressures and the power unit highly accurate in its It will also be apparent that as piston l5 approaches the limit of projectile movement from hydraulic pressure, the unloader valve rod .38 will strike the abutment disc 34 to unseat the hydraulic valve 23 and release pressure forward of the piston [5 without damaging or interfering with the operation of the double check valve 28. Upon release of pedal pressure the valve cage 28 and the valve 23 will also be opened by back pressure of fluidin the brake lines, to release the brakes and permit compensation.

From the unitized sectional arrangement of the differential pressure motor I0, it will be obvious that [in cases where such high pressures are not required, a single power unit composed of merely the stampings 11 and can be substituted for the dual units by simply securing the one unit to the enlarged end of the hydraulic cylinder I l and shortening the piston rod and piping accordingly. From this, arises the manufacturing advantage of the parts being interchangeable for dual or single motors, each of which can be readily assembled into a complete unit from parts carried in stock.

01" course it will be apparent that various changes in the arrangement of parts may be resorted to without departing from the spirit of the invention and the scope of the appended claims.

I claim:

1. A hydraulic cylinder for hydraulic brakes, a-

piston therefor having a fluid port, a valve behind said piston and cooperating with said port to trap fluid ahead of the piston, said cylinder having an inlet for fluid under pressure behind said valve, an axially movable rod engageable with said valve for moving the valve against said 7 piston to close said port and to move the piston forward in the cylinder, and means carried by said piston and movable through said port and relative to said valve to engage and open said valve when the piston has been moved away from said rod under the influence of fluid under pressure behind said valve and is near to the limit of its forward movement.

2. A device for use with hydraulic brakes comprising a hydraulic cylinder having an abutment, a piston in the cylinder and having a fluid port, a perforated sleeve projecting forward from the piston in alignment with said port, a normally open valve on the rearward side of said piston for closing said port when the piston is moved forwardly in the cylinder to apply brakes and an unloader rod slidable in said sleeve relative to said valve to move rearwardly in said port and engage and open said valve when said piston nears the limit of its forward movement and the forward end of the rod engages said abutment.

3. A hydraulic cylinder for hydraulic brakes having an outlet with a two-way check valve positioned therein, a piston in said cylinder with a fluid port, a rubber cup for said piston with a hole aligned with said port, a metallic cup forming a seat for a spring seated on said rubber cup, a perforated sleeve secured to said metallic cup and extending axially thereof, a valve cooperating with said port to trap fluid ahead of said piston,

a ported partition in the forward outlet end of said cylinder, a piston return spring on one side of said partition, a valve spring on the other side of said partition for said two-way check valve, and an unloader rod slidable in said sleeve to engage and open said piston valve when said piston moves said rod into engagement with said partition, I

4. The combination with a fluid medium differential pressure power chamber having a fluid piston and a piston rod, a hydraulic cylinder secured to one end of said cylinder and having a hydraulic piston therein with a fluid port, a valve cooperating with said port to trap fluid ahead of said hydraulic piston, and means for adjustably connecting said piston rod to said fluid piston to alter its relationship with said valve.

5. The combination with a pair of power chambers for power brakes, each having a piston therein, a hollow piston rod connecting said pistons and having a plug adjustable lengthwise therein, a hydraulic cylinder secured to one of said chambers and having a hydraulic piston therein with a fluid port, a valve cooperating with said port to trap fluid ahead of said hydraulic piston, and a solid piston rod extending through said hollow piston rod with one end in cooperative relation to said valve and its other end engaging said adjustable plug.

6. Brake operating means comprising a master cylinder having a foot pedal, a diflerential fluid pressure power engine having a piston and piston rod, a hydraulic cylinder secured to said engine and having a hydraulic piston therein with a fluid port, a pipe line connecting the master cylinder to the hydraulic cylinder at the rear of said hydraulic piston, means cooperating with said port to trap liquid ahead of said piston upon a projectile stroke thereof and to open said port upon retractile stroke of said hydraulic piston,

- said hydraulic piston being moved in a projectile stroke either by said differential piston rod or by pumping or "fanning said foot pedal to create hydraulic pressure behind said hydraulic piston, and unloading means adapted to equalize presport to-trap liquid'ahead of said piston upon a projectile stroke thereof and to open said port upon retractile stroke of said hydraulic piston, said hydraulic piston being moved in a projectile stroke either by differential fluid pressure operating said piston rod or by "pump or "fanning" said foot pedal to create hydraulic pressure behind said hydraulic piston, and unloader rod in said hydraulic cylinder adapted to engage and unseat said valve when said hydraulic piston is moved away from the end of said differential piston rod upon increase of hydraulic pressure behind said hydraulic piston.

8. Brake operating means comprising a master cylinder having afoot pedal, a differential fluid pressure power engine having a piston and piston rod, a hydraulic cylinder secured to said engine and having a hydraulic piston therein with a liquid port, a pipe line connecting the master cylinder to the hydraulic cylinder at the rear of said hydraulic piston, a valve cooperating with said port to trap liquid ahead of said hydraulic piston upon a projectile stroke thereof and to open said port upon retractile stroke of said hydraulic piston, said hydraulic piston being moved in a projectile stroke either by said differential piston rodpr by pumping" or "fanning" said foot pedal to create hydraulic pressure behind said hydraulic piston, and an unloader rod slidably mounted on said hydraulic piston and adapted to engage a part of said hydraulic cylinder to be moved relatively to engage and unseat said valve when said hydraulic piston is moved by hydraulic pressure away from the end of said differential piston rod upon increase of hydraulic pressure behind said hydraulic piston.

9. The combination with a master cylinder having foot pedal, a differential and fluid pressure power engine having a piston and piston rod. a hydraulic cylinder secured to said engine and having a hydraulic piston therein with a fluid port, a pipe line connecting the master cylinder to the hydraulic cylinder at the rear of said hydraulic piston, a rubber cup for said hydraulic piston with a hole aligned with said port, a metallic cup seated upon said rubber cup, a perforated sleeve secured to said metallic cup and extending axially thereof in alignment with said port, an unloader rod slidable in said sleeve, a valve cooperating with said port to close the same upon being projected either by an increase in hydraulic pressure or by projectile movement of saiddifferential piston rod, and a ported partition in the forward outlet end of said cylinder adapted to be engaged by said unloader rod to move the latter against said valve to open the same when the hydraulic piston has been moved near the end of the projectile stroke and away from said diiferentiai piston rod-by a build-up of hydraulic pressure behind said hydraulic piston.

10. The combination with a diflerential pressure power engine having a fluid piston and piston rod, a hydraulic cylinder secured thereto and having a hydraulic piston therein with a fluid port, a valve cooperating with said port to trap fluid ahead of said hydraulic piston upon a projectile stroke thereof and to open said port upon retractile movement of said piston, said valve being moved independently of said piston upon fluid pressure build-up on the piston rod side of said valve to close said port and to move said piston forwardly independently of said differential piston rod, and an unloader rod in said hydraulic cylinder adapted toengage and unseat said valve upon projectile stroke of said hydraulic piston induced by a hydraulic pressure build-up.

JOHN R. ALMOND.

Number Name Date 697,140 Goldschmidt Apr. 8, 1902 2,292,916 W'heelon Aug. 11, 1942 2,332,340 Price Oct. 19, 1943 10 2,345,811 Harp Apr, 4, 1944 2,349,416 Freeman May 23, 1944 2,379,299 Heintz' June 26, 1945 FOREIGN PATENTS 15 Number Country Date 504,278 Great Britain Apr. 19,1939

10 REFERENCES CITED" The following references are of record in the file of this patent:

UNITED STATES PATENTS 

